If you have a notebook computer, you have two mostly identical tabs — Battery and Power Adapter — in your Energy Saver System Preferences pane. The Battery tab controls your notebook Mac’s behavior when it’s running on battery power (not plugged in); the Power Adapter tab controls its behavior when it is plugged in.
If you have a desktop Mac, you won’t have tabs, but you do have most of the same controls, including a pair of sliders that control sleep times for your computer and display. To enable Computer or Display sleep, move the appropriate slider to the desired amount of time. You can choose any number between 1 minute and 3 hours or turn off either type of sleep entirely by moving its slider all the way to the right, to Never.
Setting the display to sleep is handy if you want your Mac to keep doing what it’s doing but you don’t need to use the monitor. And if you’re a notebook user, Display Sleep will save you battery power.
To wake up your Mac from its sleep, merely move your mouse or press any key. Sometimes moving the mouse or a finger on the trackpad won’t wake a sleeping Mac, but a keystroke will. So try both (or all three) before you give up.Below the Sleep sliders are some check boxes for other useful energy settings, such as the following:
- Put the Hard Disk(s) to Sleep When Possible: Enabling this option forces your hard drive to sleep after a few minutes of inactivity. It’s not a particularly useful feature on a desktop Mac, but if you have a laptop, letting your hard drive sleep when it’s idle will save you some battery power.
- Wake for Wi-Fi Network Access: Enable this option if you want your Mac to wake up automatically for Wi-Fi network access.
If you have a laptop, you’ll have some additional options, including
- Slightly Dim the Display While on Battery Power (Battery tab): The display dims slightly and uses less power when running on the battery.
- Enable Power Nap while on Battery Power (Battery tab): This option allows your Mac to check for new email, calendar, and other iCloud updates while it’s sleeping.
- Enable Power Nap While Plugged into a Power Adapter (Power Adapter tab): This option allows your Mac to back up to Time Machine as well as check for new email, calendar, and other iCloud updates while it’s sleeping.
- Prevent Computer from Sleeping Automatically When the Display Is Off (Power Adapter tab): Prevents sleep when the lid is closed and the display is off.
- Show Battery Status in the Menu Bar: This option adds a little battery-status indicator icon and menu.
